Vitamin D deficiency more likely a risk factor for TB than its consequence: Meta-analysis

New meta-analysis suggests that vitamin D deficiency is a risk factor for TB, not something that is caused by the condition, while the role played by ethnicity in this relationship merits further investigation.

Several studies have linked TB and vitamin D deficiency (VDD). To determine how strong the link is, researchers from the Beijing Chest Hospital and Capital Medical University conducted a meta-analysis of published papers related to TB and Vitamin D.

“All properly controlled studies published in English on vitamin D and TB were potentially eligible for inclusion in our meta-analysis. We excluded reviews, meeting abstracts, and case-only studies,”​ they wrote.

From 723 potentially eligible articles, researchers narrowed them down to 38 papers due its relevance to the topic.

Of these, 25 studies concerning 3,599 TB cases and 3,063 control subjects, found that vitamin D level was significantly lower in TB patients versus controls, and VDD was associated with an increased risk of TB.

Furthermore, VDD was significantly associated with an increased risk of developing active TB among people with latent TB infections (LTBI).

Anti-TB treatment

Three studies with 224 TB patients receiving one to four months of anti-TB treatments, and four studies with 391 TB patients receiving a full course of anti-TB treatment revealed that anti-TB treatment did not affect vitamin D level.

In addition, four studies with 327 TB cases after completion of anti-TB treatment and 592 control subjects without TB showed that patients still had a significantly lower vitamin D level after completion of treatment than controls.

“All of these results pointed to the fact that VDD is more likely a risk factor for TB. This possibility was further strengthened by our results that anti-TB treatment did not significantly affect vitamin D level in TB patients receiving the treatment and that TB subjects after completion of anti-TB treatment still had a significantly lower vitamin D level than control subjects without TB,”​ wrote the researchers.

Overall, the meta-analysis showed number of factors that suggested a link between vitamin D deficiency and the risk of TB.

However, the researchers concluded that more studies are needed to determine whether vitamin D supplementation is beneficial to TB prevention and treatment.

"Our analysis revealed a significantly lower vitamin D level in TB subjects and that VDD was associated with more risk of TB. VDD is more likely a risk factor for TB than its consequence, and more studies are needed to determine whether vitamin D supplement is beneficial to TB prevention and treatment,"​ they wrote.

“​In the subgroup analysis, although we found similar results for the Asian population, such an association was lacking in the African population even when we excluded studies where cases and controls had other diseases such as HIV and diabetes, or where the control subjects had LTBI. This suggested the possibility of ethnic difference in the role of vitamin D in TB that warrants further investigation.”​